Halogenated acetals as flame retardants for polyurethane foams

ABSTRACT

A new group of halogenated acetals is disclosed. These acetals, which are derived from the reaction of 2,4,4,4-tetrachlorobutanol with an aldehyde, are useful flame retardant additives for polyurethane foam and other polymeric materials.

1 1 HALOGENATED ACETALS AS FLAME RETARDANTS FOR POLYURETHANE FOAMS [75] Inventors: John S. Babiec, Jr.; Richard ,1.

Turley, both of Orange, Conn.

[731 Assignee: Olin Corporation, New Haven,

Conn.

[22] Filed: Sept. 24, 1973 [21] Appl. No.: 400,385

[52] US. CL... 260/25 AJ, 260/457 R, 260/611 A,

[51] Int. Cl... C08g 51/58, C08g 22/44, C07c 43/30 [58] Field ofSearch 260/25 AJ, 615 A,45.7 R

[56] References Cited UNITED STATES PATENTS 2,556,905 6/1951 Copenhaver 260/615 A 2.579.021 12/1951 Brezesinska 260/615 A 2,782,177 2/1957 Fischer 260/615 A 1 1 Oct. 22, 1974 2,802,879 8/1957 Guest 260/615 A 3.023.250 2/1962 Montugnn 260/615 A 3,137,661 6/1964 Rose 260/615 A 3,413,271 11/1968 Weesncr 260/615 A 3,660,502 5/1972 Case 260/615 A 3.784.612 1/1974 Vogt 260/615 A Primary ExaminerDona1d E. Czaja Assistant ExaminerC. Warren lvy Attbrney,Agent, or Firm- F. A. lskander; T. P. ODay [57] ABSTRACT A new group of halogenated acetals is disclosed These acetals, which are derived from the reaction of 2,4,4,4-tetrachlorobutanol with an aldehyde, are useful flame retardant additives for polyurethane foam and other polymeric materials.

6 Claims, N0 Drawings HALOGENATED ACETALS AS FLAME RETARDANTS FOR POLYURETHANE FOAMS This invention relates to a new group of halogenated acetals and to the use of these acetals as flame retardants in polymeric compositions, particularly polyurethane foam.

It is known to prepare acetals by reacting an alcohol with an aldehyde as disclosed in U.S. Pat. No. 2,668,862. Halogenated acetals based on ethyl alcohol are also known in the art. See for example U.S. Pat. No. 2,578,021. Such compounds are utilized in the production of insecticides and fungicides.

Now, in accordance with the invention, a new group of halogenated acetals has been found which are products of condensing 2,4,4,4-tetrahalobutanol with a monoor dialdehyde. Further according to the invention, these acetals are utilized as flame retardant additives in polymeric compositions, especially polyurethane foam.

Generally speaking, a wide range of aldehydes may be employed in preparing the acetals of the invention. This includes, for example, the heterocyclic aldehydes, such as furfural, and various substituted aliphatic and aromatic aldehydes such as meth'oxyacetaldehyde, salicylaldehyde, and piperonal. Also, the halogen in the tetrahalobutanol reactant can be chlorine, bromine or a mixture thereof. However, in accordance with the preferred embodiments of the inventiomthe acetals are derived from 2,4,4,4-tetrachlorobutanol and-a halogenfree or halogen-substituted aliphatic, aromatic, or aliphatic-aromatic aldehyde. These acetals may be represented by Formula I as follows:

X Rt CH0),

wherein X, a, R, and n have the significance indicated above. Where the R radical in the aldehyde represents an alkyl group, this usually contains 1-12, and-preferably l-4, carbon atoms, such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; where the R radical is alkene, this again usually contains 2-12, and preferably 2-4, carbon atoms such as ethylene, propene, butene, and dodecene; where R is aryl, this usually contains 6-12, and preferably 6,carbon atoms such as phenyl, biphenyl, and naphthyl; where R is alkaryl, this usually contains 7-12, and preferably 7, carbon atoms such as tolyl, xylyl, ethylphenyl, isopropyphenyl, and tertiary butylphenyl; and where R is aralkyl, this usually contains 7-12. and preferably 7, carbon atoms such as benzyl, phenylethyl, and phenylhexyl.

The following list is illustrative of the aldchydes which may be used in preparing the acetals of the invention:

formaldehyde 4 ,4 A -tnchlumhutyrultlchyde acetuldehyde Z-hromopropionaldchyde propionaldehyde .l-hromopropionaldehyde butyraldehyde 4.4.4-trihromohutyraldehyde acrylaldehyde bromal crotonaldehyde acrolein chlo roacetaldehydc benzaldehyde bromoacetaldehyde tolualdehyde dichloroacetaldehyde invention: dibromoacetaldehyde m-bromobenzaldehyde chloral 2.4-dichlorobenzaldeh yde Z-chloropropionaldehyde glyoxal 3-chloropropionaldehyde succinaldehyde 2,3-dichloroprionaldehyde te rephthaldehyde In preparing monoacetals of Formula I, one mole of a monoaldehyde of Formula 11 wherein n 1 is reacted with two moles of 2,4,4,4-tetrachlorobutanol; whereas, to prepare diacetals of Formula 1, one mole of a dialdehyde of Formula 11 wherein n 2 is reacted with four moles of the tetrachlorobutanol. These reactions are illustrated in Equation [11 as follows:

Ill

wherein X, a, R and n have the above significance.

The reaction is generally carried out in the presence of an acidic catalyst, e.g., sulfuric acid, and preferably an inert solvent such as benzene. Water is removed from the reaction medium as it is formed by any suitable means such as by co-distillation with the solvent using a Dean-Stark trap. Alternatively, magnesium sulfate may be added tothe reaction mixture to absorb the water. Depending on the reactivity of the particular aldehyde used, the reaction may be carried out at room temperature or at moderately elevated temperatures, e.g., the reflux temperature for the solvent if such is used. If desired, the reaction may be effected at subatmospheric pressure which would enable distilling off the water at reduced temperatures. Completion of the reaction is signaled when no more water is produced. At this point, the solids if any, i.e., MgSO are filtered out, the acid catalyst is removed by washing with a dilute, aqueous base solution, and any volatiles, i.e., solvent if such is used, are removed by distillation at reduced pressure.

In accordance with the more preferred embodiments of the invention, a lower, saturated aliphatic monoaldehyde is employed in preparing acetals having Formula IV as follows:

xnuinrocnirincicn ccn wherein R is hydrogen or alkyl of 1-3 carbon atoms, a is an integer from 1 to 3 and, X is as signified above. Illustrative of the preferred acetals represented by Formula IV are:

bis( 2,4,4,4-tetrachlorobutyl) 4,4,4-trichlorobutyral bist 2,4,4,4-tetrachlorobutyl) 3-chloropropional bist 2,4,4,4-tetrachlorobutyl) chloroacetal bis( 2,4,4,4-tetrachlorobutyl) 2-chloropropional bist 2,4,4,4-tetrachlorobutyl) 2,3-dichloropropional bis( 2,4,4,4-tetrachlorobutyl) dichloroacetal bis( 2,4,4,4-tetrachlorobutyl) 4,4,4-tribromobutyral bist2,4,4,4-tetrachlorobutyl) 3-bromopropional bist2.4,4,4-tetrachlorobutyl) dibromoacetal The most preferred acetals of the invention are those of formula 1V above in which R is alkyl of 2-3 carbons and X is chlorine, such as bis(2,4,4,4-tetrachlorobutyl) 4,4,4-trichlorobutyral and bist 2,4,4,4- tetrachlorobutyl) 3-chloropropional.

The acetals of the invention are utilized as flame retardant additives in polymeric compositions. They are of particular utility, according to the invention, in preparing flame retardant polyurethane foam which may be flexible, semi-rigid or rigid.

1n the preparation of the polyurethane foam, either the so-called one-shot method" or the semiprepolymer technique may be employed, the one-shot method being preferred. Any combination of polyols, including polyester polyols and polyether polyols, organic polyisocyanates, foaming agent, catalyst, and other reactants capable of forming a cellular urethane material may be used in preparing the foam. Typical formulations are described in U.S. Pat. No. 3,072,582, issued Jan. 8, 1963, and Canadian Pat. No. 705,938 which issued mar. 16, 1965.

While, as indicated above, both polyether and polyester polyols can be employed in the practice of this invention, preferred embodiments utilize polyether polyols in the preparation of the polyurethane foam forming reaction mixture. Any suitable polyether polyol may be used for this purpose. These polyether polyols usually have a hydroxyl number for example from about 25 to about 800.

The polyether polyols include for example oxyalkylated polyhydric alcohols having a molecular weight range of about ZOO-10,000 and preferably between about 2508,000. These oxyalkylated polyhydric alcohols are generally prepared by methods well known in the art such as by reacting, in the presence of an alkaline catalyst, a polyhydric alcohol and an alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide, epichlorohydrin, and mixtures of these alkylene oxides, using either random or step-wise addition.

polyhydric alcohols suitable for use in preparing the polyether polyols include ethylene glycol, pentaerythritol, methyl glucoside, propylene glycol, 2,3-butylene glycol, 1,3-butylene glycol, l,5-pentane diol, 1,6- hexane diol, glycerol, trimethylolpropane, sorbitol, sucrose, dextrose, mixtures thereof and the like. 1f desired, a portion or all of the polyhydric alchol may be replaced with another compound having at least two reactive hydrogen atoms, such alkyl amines, alkylene polyamines, cyclic amines, amides, and polycarboxylic acids. Suitable alkyl amines and alkylene polyamines include methylamine, ethylamine, propylamine, butylamine, hexylamine, ethylenediamine, 1,6- hexanediamine, diethylenetriamine, and the like. Also, such cyclic amines as piperazine, 2-methylpiperazine and 2,5-dimethylpiperazine may be used. Amides, such as acetamide, succinamide and benzensulfonamide constitute a further class of such reactive hydrogen compounds. A still further class of such reactive hydrogen compounds is the diand polycarboxylic acids, such as adipic acid, succinic acid, glutaric acid, aconotic acid, diglycollic acid, and the like. It will be rec ognized that the reactive hydrogen compound can be one containing different functional groups having reactive hydrogen atoms, such as citric acid, glycollic acid, ethanolamine, and the like. Aromatic polyamines such as toluene diamine may also be employed. Mixtures of oxyalkylated polyhydric alcohols are also suitable for use in the process of this invention.

The organic polyisocyanates used in the preparation of the polyurethane foams include toluene diisocyanate, such as the 4:1 mixture or the 65:35 mixture of the 2,4- and 2,6-isomers, ethylene diisocyanate, propylene diisocyanate, methylene-bis-4-phenyl isocyanate, 3,3'-bitoluene-4,4-dissocyanate, hexamethylene diisocyanate, naphthalene-l,5diisocyanate, polyphenylene polymethylene isocyanate, mixtures thereof and the like. The preferred organic polyisocyanate is toluene diisocyanate. The amount of isocyanate employed in the process of this invention should be sufficient to provide at least about 0.7 NCO group per hydroxyl group present in the reaction system, which includes the polyol as well as any additive or foaming agent employed. An excess of isocyanate compound may be conveniently employed; however, this is generally undesirable due to the high cost of the isocyanate compounds. lt is preferable, therefore, to employ sufficient isocyanate to provide no greater than about 1.25 NCO groups per hydroxyl group, and preferably between about 0.9 and about 1.15 NCO groups per hydroxyl group. The ratio of NCO to OH group times is referred to as the index."

The polyurethane foams are prepared in the presence of a foaming agent which may be any of those known to be useful for this purpose. Illustrative are water and organic foaming agents containing up to about seven carbon atoms such as the halogenated hydrocarbons, lower molecular weight alkanes, alkenes, ethers, and mixtures thereof. Typical halogenated hydrocarbons include, but are not limited to, monofluorotrichloromethane, dichlorofluoromethane, difluorodichloromethane, 1 ,1 ,2-trichloro-1 ,2,2-trifluoroethane, dichlorotetrafluoroethane, ethyl chloride, methylene chloride, chloroform, and carbon tetrachloride. Other useful foaming agents include lower molecular weight alkanes, alkenes and ethers such as methane, ethane, ethylene, propane, propylene, pentane, hexane, heptane, ethyl ether, diisopropyl ether, mixtures thereof, and the like. The amount of foaming agent employed may be varied within a wide range. Generally, however, the halogenated hydrocarbons are employed in an amount from about 1 to about 50, and preferably about 5-35, parts per 100 parts by weight of the polyol, and generally water is employed in an amount from about 1.0 to 6.0 parts by weight per 100 parts by weight of the polyol.

The polyurethane foams are prepared in the presence of a catalytic amount of a reaction catalyst. The catalyst employed may be any of the catalysts known to be useful for this purpose, such as tertiary amines and metallic salts, particularly stannous salts, and mixtures thereof. Typical tertiary amines include, but are not limited to, the following: N-ethyl morpholine, N- hydroxyethyl morpholine, triethylene diamine, triethylamine and trimethylamine. Typical metallic salts include, for example, the salts of antimony, tin and iron, e.g., dibutyltin dilaurate, stannous octoate, and the like. Any catalytic proportion of catalyst or catalyst mixture may be employed such as between about 0.1 and about 3.0 percent, and preferably between about 0.5 and about 2.5 percent, by weight of the polyol.

It is preferred in the preparation of the polyurethane foams of the invention to employ minor amounts of a conventional surfactant in order to further improve the cell structure of the polyurethane foam. Typical of such surfactants are the silicones and the siloxaneoxyalkylene block copolymers. US. Pat. No. 2,834,748 and T. H; Ferrigno, Rigid Plastic Foams (New York: Reinhold Publishing Corp., 1963) pages 38-42, disclose various surfactants which are useful for this purpose. Generally up to 2 parts by weight of the surfactant are employed per 100 parts of the polyol.

1n the preparation of flame retardant polyurethane foam, the acetal additives of the invention are usually incorporated in the polyurethane forming reaction mixture before foaming. Conveniently, they are first mixed in with the polyol reactant, and the other ingredients used in making the foam then added to this mixture. Any suitable proportion of these additives may be used which is effective in reducing the flammability of the foam without otherwise interferring with the foaming reaction or materially altering the properties of the re-- sulting foam. For example, the acetals may be used in a proportion of about 5-45, preferably about 40, and still more preferably about l535, parts per every 100 parts by weight of total polyol which is employed in preparing the polyurethane foam.

in accordance with one preferred embodiment of the invention, increased'flame retardancy is achieved by incorporating in the foam forming formulation, prior to foaming, a co-additive mixture of an acetal as described above and antimony oxide or antimony oxyhalide. By combining both additives in the foam, a synergistic flame retardant effect is attained. Thus the use of the antimony co-additive is particularly preferred in foam applications requiring a very high degree of flame retardancy.

The antimony oxide co-additive can be for example antimony trioxide Sb O or antimony tetraoxide Sb O and'the antimony oxyhalide can be for example antimony oxychloride e.g., SbOCl or Sb O CL or antimony oxybromide. The most preferred antimony co-additive is antimony t'rioxide.

The antimony co-additive can be employed in any suitable proportion which enhances the flame retardant effect of the acetal without otherwise detrimentally affecting the foaming reaction or the properties of the resulting foam. For example, it may be employed in a proportion ranging from about 1 to about 25, and pref erably about 3-15, parts per every 100 parts by weight of total polyol used in making the foam.

The acetals of the invention have all of the basic attributes which are generally sought after in a flame retardant additive for polyurethane foam. Thus they are simple to prepare and relatively inexpensive to use in foam making. They are also inert materials which exert no adverse effect on the foam or materially alter its physical properties. Finally, polyurethane foams incorporating these acetals have a high degree of flame retardancy, and they are rated self-extinguishing according to'the flammability test described in ASTM D-l692-68. As such, these foams can be utilized in a rapidly increasing field of applications in which fireresistant materials are required. These include, for example, insulation for buildings and storage vessels, furniture upholstering, mattresses, carpet underlayment and so forth.

The following examples are provided to illustrate the invention. In these examples, all parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 Bis( 2,4,4,4-tetrachlorobutyl) 3-chloropropional In a reaction vessel equipped with a thermometer and a mechanical agitator, 106 gms. of 2,4,4,4- tetrachlorobutanol were dissolved in mls. of benzene. The solution was then saturated with anhydrous hydrochloric acid at 0C. and in the presence of 30 gms. of anhydrous magnesium sulfate. An ice bath was used to control the temperature. Acrolein was thereafter added to the mixture drop-wise and at such a rate as to maintain the temperature inside the reaction vessel below 2C. After a total of 14 gms. of acrolein were added, the mixture was agitated for an additional hour while being maintained within a temperature range of O2C. It was then allowed to stand at room temperature for three days. The benzene was then removed by distillation under partial vacuum. Any residual water present was removed by adding a fresh quantity of benzene and stripping this off with the residual water at reduced pressure. The remaining reaction product mixture was dissolved in benzene followed by filtration to remove undissolved solids. After stripping off the benzene, the bis( 2,4,4,4-tetrachlorobutyl) 3 -chloropropional product was recovered from the reaction mixture by extraction with a solvent mixture of 360 mls. methanol and 240 mls. water. The lower acetal phase was separated from the methanol-water system and stripped of volatiles by heating at 4550C. and 0.2 m.ms. of mercury pressure. The acetal product thus obtained was a light brown liquid. The structure of bisf2,4,4,4-tetrachlorobutyl) 3-chloropropional was confirmed by nuclear magnetic resonance as follows, based on the emperical formula C H, Cl O Calculated: 26.51% carbon, 3.03% hydrogen, and

64.03% chlorine. Found: 27.16% carbon,

63.68% chlorine.

EXAMPLE 2 2.91% hydrogen, and

fonic acid, 30 gms. of anhydrous magnesium sulfate,

and mls. of benzene was stirred at room temperature for 64 hours. Then, after the resulting mixture was freed of solids by filtration, the benzene was removed by distillation at sub-atmospheric pressure. A chloroform solution of the residue was successively washed with water, a saturated aqueous sodium bicarbonate solution, and then again with water. Solvent'and most of the unreacted alcohol were removed by vacuum distillation. A carbon tetrachloride solution of the residue was passed through a 50 gms. column of silica gel to remove remaining traces of alcohol. A light brown liquid acetal product was then recovered after stripping off the carbon tetrachloride solvent. The structure of bisf 2,4,4,4-tetrachlorobutyl) n-butyral was confirmed by nuclear magnetic resonance, gel permeation chromatography, and infrared analysis.

EXAMPLE 3 Bisf 2,4,4,4-tetrachlorobutyl) 2,4-dichlorobenzal A solution of 424 gms. of 2,4,4,4-tetrachlorobutanol in 300 mls. of benzene was mixed with 175 mls. of 2,4- dichlorobenzaldehyde and mls. of concentrated sulfuric acid. Using a Dean-Stark water trap to remove the water as it is formed, the mixture was refluxed until no more water appeared. The acetal product was separated from the reaction mixture by extraction with a methanol-water solvent system. Thus separated, the acetal product was dissolved in carbon tetrachloride and then successively washed with an aqueous 20 percent solution of sodium bisulfite, water, percent aqueous potassium carbonate, and finally again with water. The washed solution was dried over magnesium sulfate, and after being substantially decolorized with charcoal, it was freed of volatiles by heating at reduced pressure. The acetal product thus recovered was a light brown syrup, and the structure of bis( 2,4,4,4- tetrachlorobutyl) 2,4-dichlorobenzal was confirmed by infrared analysis.

EXAMPLE 4 Flame Retardant Polyurethane Foam A flexible polyurethane foam was prepared from the following ingredients in the indicated proportions:

Z.4-/2,6-isomers) This material, purchased under the trademark Dabco 33LV, contains about 33% triethylene diaminc, the balance being substantially dipropylene glycol.

"This surfactant, purchased under the trademark DC-l90. is a block copolymer of polydimethylsiloxane and a polyester resin.

To the above mixture, 25 gms. of bis( 2,4, 1,4- tetrachlorobutyl) 3-chloropropional were added. Procedurally, this was blended in with the oxypropylated glycerin before adding the other ingredients of the foam forming reaction mixture. The total mixture was then poured into an open-top, cardboard box and allowed to expand into a flexible foam block which was oven cured at 110C. for minutes.

The flammability of the foam was tested in accordance with the test described in ASTM D-l692-68. The foam was found to be self-extinguishing, with an extent of burning limited to an average of 4.5 inches, using foam samples 6 inches in length. The burning rate averaged 3.5 ins/min.

For purposes of comparison, another foam was prepared as described above except for the exclusion of the 2,4,4,4-tetrachlorobutyl) 3-chloropropional from the foam forming reaction mixture. The resulting foam burned through at the average rate of 6.3 ins/min.

EXAMPLE 5 Flame Retardant Polyurethane Foam The identical procedure of Example 4 was followed except that there were also included in the foam forming reaction mixture 10 gms. of antimony trioxide. The resulting foam was rated self-extinguishing with a burning rate average of 2.8 ins/min. The extent of burning was limited to an average of 2.2 inches. This example demonstrates the synesgistic burn resistance effect which obtains by using a co additive mixture of an acetal of the invention and antimony trioxide to impart flame retardant properties to polyurethane foam.

What is claimed is:

l. A polyurethane foam prepared from a reaction mixture comprising, as a flame retardant additive, a halogenated acetal represented by the formula X is chlorine, bromine, or a mixture thereof,

a is an integer of O to 4,

R is selected from the group consisting of hydrogen,

and alkyl group of l-l2 carbon atoms, and an alkene group of 2-12 carbon atoms, and n is l or 2.

2. A polyurethane foam prepared from a reaction mixture comprising, as a flame retardant additive, a halogenated acetal as defined in claim 1 wherein a is an integer from 1 to 3, R is hydrogen or alkyl group of l-3 carbons atoms, and n is l.

3. A polyurethane foam prepared from a reaction mixture comprising, as a flame retardant additive, a halogenated acetal as defined in claim 2 wherein X is chlorine and R is alkyl of l-3 carbon atoms.

4. The polyurethane foam of claim 3 wherein said reaction mixture also comprises a flame retardant coadditive selected from an antimony oxide, antimony oxychloride and antimony oxybromide.

5. A polyurethane foam prepared from a reaction mixture comprising, as a flame retardant additive, a halogenated acetal as defined in claim 1 wherein the acetal is bis(2,4,4,4-tetrachlorobutyl)4,4,4,-trichlor0- butyral. v

6. A polyurethane foam prepared from a reaction mixture comprising, as a flame retardant additive, a halogenated acetal as defined in claim 1 wherein the acetal is bis( 2,4,4,4,-tetrachlorobutyl)3-chloropropional. 

1. A POLYURETHANE FOAM PREPARED FROM A REACTION MIXTURE COMPRISING AS A FLAME RETARDANT ADDITIVE, A HALOGENATED ACETAL REPRESENTED BY THE FORMULA
 2. A polyurethane foam prepared from a reaction mixture comprising, as a flame retardant additive, a halogenated acetal as defined in claim 1 wherein a is an integer from 1 to 3, R is hydrogen or alkyl group of 1-3 carbons atoms, and n is
 1. 3. A polyurethane foam prepared from a reaction mixture comprising, as a flame retardant additive, a halogenated acetal as defined in claim 2 wherein X is chlorine and R is alkyl of 1-3 carbon atoms.
 4. The polyurethane foam of claim 3 wherein said reaction mixture also comprises a flame retardant co-additive selected from an antimony oxide, antimony oxychloride and antimony oxybromide.
 5. A polyurethane foam prepared from a reaction mixture comprising, as a flame retardant additive, a halogenated acetal as defined in claim 1 wherein the acetal is bis(2,4,4,4-tetrachlorobutyl)4,4,4,-trichlorobutyral.
 6. A polyurethane foam prepared from a reaction mixture comprising, as a flame retardant additive, a halogenated acetal as defined in claim 1 wherein the acetal is bis(2,4,4,4,-tetrachlorobutyl)3-chloropropional. 